Transcript Graphing the Line of Best Fit

Graphing the Line
of Best Fit
Sensei
By: Gene Thompson, PHS
Edited: John Boehringer, PHS
What to expect:
• This short PowerPoint will run you through how to
enter data into the calculator.
• This is meant to serve as a supplement to class, and
thus there is no example data included. Only the
steps are shown.
• Remember, it is always recommended that you
write your own notes for this, rather than simply
copying what is presented here!
Formatting
• S
This represents a button on the calculator.
• Menus will be in bold.
• Choices from a menu will have a (1) number.
Step 1: Enter your data
Press S
→ 1.Edit…
Enter your data in the lists provided. Typically, (x) is in
the L1 list, and (y) is in the L2 list.
Special Note
Note: If your lists are missing or out of order, you can
fix this by pressing S
→ 5.SetupEditor and pressing
enter. It will say “Done” when you finish.
Step 2: Linear Regression
Press S → CALC → 4.LinReg(ax+b)
You are now asking the calculator to match the best
line to your data.
Step 3: Specify your lists
You have to tell the calculator which lists have your xand y-data. Press `1 for L1, , and ` 2 for L2. If your x- and
y-data items are NOT in L1 and L2 respectively, use
whatever list numbers they are in.
You must enter a comma between the lists. This is next
to the () buttons.
Step 4: Include Y1
This step is optional, but useful. You can ask the
calculator to put your equation into ! so you don’t
have to type it in. Press v → Y-VARS → 1.Function. In
the next menu, choose Y1.
Step 5: Hit Enter
Once your screen looks like the left, hit e.
The calculator will give you the equation in that form.
Just note that a is the slope (goes in front of x), and b
is the y-intercept. Round your answer appropriately.
Bonus: Diagnostics
If you want to turn on the diagnostics, so that you can
get the correlation coefficient (the R values), press `0
to go to the catalog, and scroll down to the D’s (you
can jump there by hitting i, which is the D key when a is
pressed). Choose DiagnosticOn from the menu, then
hit enter. When it says “Done” you have turned the Rvalues on.
Bonus: Diagnostics
After doing that and running the linear regression, you
will see some extra values. These aren’t necessary,
but they let you know how good your data is.
Checking the Graph
Now, if you want to see your graph, we first need to
turn on the plot. Press `! to get to the first plot, and turn
it on by hitting e.
Window Adjustments
Before you can see your plot, you will have to adjust the
window. Automatic option: Press Zoom 9.
Do it yourself option:
Press @ to bring up these options.
It is best to set your x-minimum and y-minimum to zero, unless
you have negative values. Set your maximums so that they
reach slightly further than the biggest values in your data.
The xscl stands for x-scale. It is
what the marks on the axis will
count by. Think of it as what you
would mark on your graph if you
were drawing it yourself. If you
were going out to 100, you
wouldn’t count by 1’s, right?
Finally: The graph!
By pressing %, you will see your data and line.
If you press !, you will notice your line’s equation was
typed in by the LinReg(ax+b) function.
The calculator
These are the buttons that we used
during this demonstration, in case you
were having trouble finding them. I
didn’t include the numbers or 2nd
Function key.